|Publication number||US7572354 B2|
|Application number||US 11/445,594|
|Publication date||Aug 11, 2009|
|Filing date||Jun 1, 2006|
|Priority date||Jan 14, 2000|
|Also published as||US6630059, US6666959, US20020020621, US20040134793, US20060219573, WO2001052307A2, WO2001052307A3, WO2001052307A9|
|Publication number||11445594, 445594, US 7572354 B2, US 7572354B2, US-B2-7572354, US7572354 B2, US7572354B2|
|Inventors||Cyprian Emeka Uzoh, Homayoun Talieh, Bulent Basol, Douglas W. Young|
|Original Assignee||Novellus Systems, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (33), Non-Patent Citations (4), Classifications (31), Legal Events (3)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This is a continuation of U.S. Ser. No. 10/744,293, filed Dec. 22, 2003, now abandoned, which is a continuation of U.S. Ser. No. 09/976,972, filed Oct. 11, 2001, now U.S. Pat. No. 6,666,959, issued Dec. 23, 2003, which is a divisional of U.S. Ser. No. 09/483,095, filed Jan. 14, 2000 , now U.S. Pat. No. 6,630,059, issued Oct. 7, 2003, all incorporated herein by reference.
The present invention relates to methods and apparatus for plating a conductive material on a semiconductor substrate. More particularly, the present invention is directed to “proximity plating” methods and apparatus for plating the conductive material on the semiconductor substrate. The substrate is plated with the conductive material as the pad and/or blade type objects are rotated in close proximity to the substrate.
A conventional process step in the manufacturing of integrated circuits and devices involves plating a conductive layer on a semiconductor substrate. Plating the substrate with the conductive material over a seed layer has important and broad application in the semiconductor industry. Traditionally, aluminum and other metals are deposited as one of many conductive layers that make up a semiconductor chip. However, in recent times, there is great interest in copper deposition for interconnects on semiconductor chips, because, compared to aluminum, copper reduces electrical resistance and allows semiconductor chips to run faster with less heat generation, resulting in a significant gain in chip capacity and efficiency.
Typically, the semiconductor substrate has been previously etched and contains many holes and/or trenches on its surface. One goal of plating is to uniformly fill the holes and trenches with the conductive material.
However, as known in the art, conventional plating methods result in “dishing” or non-planar deposition during the plating process. In
For small features with sub-micron size dimensions, existence of voids in the deposited conductive layer is a common problem. In
It is an object of the present invention to provide methods and apparatus that deposit a conductive material on a substrate with the pad or blade type objects rotating in a circular manner.
It is another object of the present invention to provide methods and apparatus that deposit a conductive material on a substrate while eliminating/reducing dishing and voids.
It is yet another object of the present invention to provide methods and apparatus that deposit a conductive material on a substrate using novel pad-anode or blade-anode assemblies.
These and other objects of the present invention are obtained by providing methods and apparatus for depositing a conductive material from an electrolyte solution to the substrate. This is achieved by providing pad or blade type objects mounted on cylindrical anodes or rollers and applying the conductive material to the substrate using the electrolyte solution disposed on or through the pads or on the blades.
An apparatus that performs such plating includes anodes and a cathode workpiece that are in close proximity of each other. The pad or blade type objects mounted on the cylindrical anodes or rollers rotate about a first axis and the workpiece may be stationary or rotate about a second axis, and metal from the electrolyte solution is deposited on the workpiece when a potential difference is applied between the workpiece and the anode.
Alternatively, the plating apparatus may include an anode plate spaced apart from the cathode workpiece. Upon application of power to the anode plate and the cathode workpiece, the electrolyte solution disposed in the plating apparatus is used to deposit the conductive material on the workpiece surface using cylindrical rollers having the pad or blade type objects.
Further, in another embodiment, the plating apparatus may include an anode plate spaced apart from cylindrical cathodes having conductive pads or blades. Upon application of power to the anode plate and the cathodes and upon rotating the cathodes in a circular direction, the conductive pads or blades make electric contact to the workpiece surface rendering it cathodic with respect to the anode plate, and metal from an electrolyte solution is deposited on the same surface.
These and other objects and advantages of the present invention will become apparent and more readily appreciated from the following detailed description of the presently preferred exemplary embodiments of the invention taken in conjunction with the accompanying drawings, of which:
The preferred embodiments of the present invention will now be described with reference to
An example of a proximity plating method and apparatus is disclosed in a U.S. application Ser. No. 09/285,621, issued Dec. 11, 2001 as U.S. Pat. No. 6,328,872 entitled “Method and Apparatus For Plating and Polishing a Semiconductor Substrate”, commonly owned by the assignee of the present invention, the contents of which are expressly incorporated herein by reference. The present invention discloses alternative embodiments.
One object of the present invention is to eliminate dishing.
As shown, the cylindrical anodes 140 a, 140 b, etc., are in partial contact with the electrolyte solution 110. In other words, the top level of the electrolyte solution 110 is below the surface of a workpiece 160 (i.e., the top level of the electrolyte solution 110 does not make direct contact with the workpiece surface when the cylindrical anodes 140 a, 140 b, etc., are stationary). Alternatively, the electrolyte solution 110 may be making contact with the workpiece 160 surface.
During operation, a voltage is applied between the cylindrical anodes 140 a, 140 b, etc., and a cathode workpiece 160. Electrical contact to the cathode workpiece 160 is made via cathode contacts 184. When the anodes 140 a, 140 b, etc., and the pad strips (or pads) 130 a, 130 b, etc., are rotating about axis 150 in either a clockwise or counterclockwise direction, and are spaced apart from the cathode workpiece 160 (the pad strips 130 a, 130 b, etc. do not make direct contact with the workpiece 160, or alternatively, make only slight contact), the workpiece 160 is plated using the electrolyte solution 110.
The anodes 140 a, 140 b, etc. and the pad strips 130 a, 130 b, etc. should preferably rotate at a rate such that the electrolyte solution 110 is continuously “picked” by the anodes 140 a. 140 b, etc., and applied/splashed onto the workpiece 160. They may all rotate in the same clockwise or counterclockwise direction or alternatively, some may rotate in one direction (i.e., clockwise) while others may rotate in the opposite direction (i.e., counterclockwise). Further, during operation, one, two, three, . . . , or all anodes 140 a, 140 b, etc., may be activated concurrently and voltages may be applied to all or only a selected number of them. Anode current densities for different anodes 140 a, 140 b, etc., may vary, and this can be used to control the uniformity of the deposited material across the workpiece 160. In addition, the length of the anodes 140 a, 140 b, etc., may all be the same or they may be different.
When the gaps between the pads 130 a, 130 b, etc., and the workpiece 160 are about 0-5 mm and contains a meniscus of electrolyte solution 110, a very high mass transport results, thereby depositing high quality metal films onto the workpiece 160. Moreover, when electric power is applied to the cylindrical anodes 140 a, 140 b, etc., and the cathode workpiece 160, a closed electrical circuit is formed through the anode assemblies 120 a, 120 b, etc., the applied/splashed electrolyte solution 110 in the gaps, and the workpiece 160. This is described in more detail below. Moreover, depending on the type, shape, and structure of the pads 130 a, 130 b, etc., the gaps may be greater than 5 mm.
The workpiece head assembly 180 may include a nonconductive, preferably circular chuck 182 with a cavity that is preferably a few millimeters deep at its center and which cavity may contain a resting pad (not shown). The workpiece 160 is loaded into the cavity, backside first, against the resting pad using a conventional type of transport or vacuum mechanism to ensure that the workpiece 160 is stationary with respect to the workpiece head assembly 180 while in use. A nonconductive retaining ring (not shown) such as an O-ring or other rubber type of seal at the periphery of the workpiece head assembly 180 and the cathode contacts 184 each push against the edge of the workpiece 160 and hold it in place. The entire back side of the workpiece 160 which pushes against the chuck 182 that is under the retaining ring is thus protected from any and all solutions, including electrolyte. Other conventional workpiece head assemblies can be used in accordance with the present invention.
As shown, the workpiece head assembly 180 faces toward the anode assemblies 120 a, 120 b, etc. The head assembly 180 may be stationary or rotate around axis 190 using a conventional motorized spindle (not shown). The head assembly 180 may also be adapted to move up and down and/or side to side in the direction of arrow 192 so that the workpiece 160 may be plated more effectively.
Instead of using the cathode contacts 184 described above, the electric potential can be applied to the workpiece 160 using a ring conductor. Further, other methods of applying the electric potential to the workpiece may be used in accordance with the present invention. For example, a liquid conductor or an inflatable tube coated with a conductive material may be used in the present invention. An example of using the liquid conductor or the conductive tube to provide the necessary electric potential is disclosed in the U.S. application Ser. No. 09/283,024, now U.S. Pat. No. 6,251,235, issued Jun. 26, 2001, entitled “Method And Apparatus For Forming an Electric Contact With a Semiconductor Substrate”, commonly owned by the assignee of the present invention, the contents of which are expressly incorporated herein by reference. What is important to note from the previous examples is that any method for providing an electric potential between the anode or anodes and the cathode workpiece can be used in the present invention.
It should be appreciated that many other designs of pad strips can also be used effectively in the present invention. What is important is that these strips cause rigorous stirring of the electrolyte at the workpiece surface. The pad strips described thus far in
In another embodiment of the present invention, the pad strips or blades 130 a, 130 b, etc., in
The anode assemblies of
The anode assembly 300 also includes pads 320 (130 a, 130 b, etc. in
The chamber 400 includes an anode plate 460 on the bottom of the chamber 400. Any known method for attaching the anode plate 460 to the bottom of the chamber 400 may be used. In the alternative, the anode plate 460 may be positioned at any other location in the chamber 400 so long as it makes physical contact with the electrolyte solution 440. The electrolyte solution 440 in the chamber 400 also makes contact with the pads 420 a, 420 b, etc. The electrolyte solution 440 can be originally fed into the chamber 400 via a reservoir (not shown) through an in-channel (not shown).
Upon application of power between the workpiece 160 via, for example, contacts 184 and the anode plate 460, and upon rotating one or more rollers 410 a, 410 b, etc. about axis 450 in either a clockwise or counterclockwise direction, the electrolyte solution 440 is continuously splashed/applied to the workpiece 160 via pads 420 a, 420 b, etc. Shafts 470 a, 470 b, etc., are used to rotate the rollers 410 a, 410 b, etc, respectively. Thus, metal is plated out of the electrolyte solution 440 onto the workpiece 160 surface. As disclosed earlier herein, rollers with blade type objects instead of pads can be used.
In another embodiment of the present invention, the pad/blade 420 a, 420 b, etc. material in
The attractive feature of the design of
Referring back to the embodiment in
In all embodiments described herein, the hardness of the pad or blade type objects is related to the relative speed of rotation of the pads or blades with respect to the workpiece.
Although both DC and pulsed power supplies can be used to apply power to the anode(s) and the workpiece, the present invention may reduce the need for pulse generating power supplies because the mechanical pulsing that is generated from the movement of the pads or blades relative to the face of the workpiece creates sufficient pulsing. This mechanical pulsing is created as a result of the workpiece being in proximity with the pads or blades as it is moved in relation to the workpiece. The benefit of the mechanical pulsing is that it improves grain size, filling efficiency of the contact holes, vias, and trenches, and copper film integrity without the need for power supplies with pulsing capabilities.
In additional to the mechanical pulsing, the anode assemblies disclosed herein can provide electrical pulsing. If the pad and/or blade materials are insulating, then the plating current density decreases as the cylindrical anode is rotating when the pad and/or blades are in their closest distance to the workpiece surface. On the other hand, when the pad/blade is not in their closest distance to the workpiece surface (i.e., the gaps in between each pad/blade) as the cylindrical anode is rotated, then the current density increases. Such pulsing is found to be beneficial for forming a high quality material on the workpiece surface.
Although deposition of a conductive material has so far been described hereinabove, those skilled in the art can use the teachings herein for etching and electroetching processes. For example, if the voltage applied between the workpiece and the anode(s) is such that the workpiece is more negative than the anode(s), then plating on the workpiece surface occurs. If the voltage is zero, then chemical etching of the conductive material on the workpiece surface occurs. If the polarity voltage is reversed, then electroetching of the conductive material from the workpiece surface can be initiated. Alternately, the apparatus disclosed herein can be used for electroless deposition of materials such as Cu, Ni, Ni—P, Co, etc. In this case, an electroless deposition solution is used rather than the electrodeposition electrolyte solution.
Although the embodiments shown thus far illustrate one workpiece, it is understood that more than one workpiece head assembly could be used with the present invention. Furthermore. each chamber described above may include various numbers of anode/roller assemblies so long as they can effectively plate a conductive layer on a workpiece surface.
In the previous descriptions, numerous specific details are set forth, such as specific materials, structures, chemicals, processes, etc., to provide a thorough understanding of the present invention. However, as one having ordinary skill in the art would recognize, the present invention can be practiced without resorting to the details specifically set forth.
Although only the above embodiments have been described in detail above, those killed in the art will readily appreciate that many modifications of the exemplary embodiment are possible without materially departing from the novel teachings and advantages of this invention.
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|U.S. Classification||204/242, 451/41|
|International Classification||C25D5/06, C25D17/14, B24B37/04, H01L21/288, C25D7/12, C25F7/00, H01L21/768, C25D7/00, C25B9/00|
|Cooperative Classification||C25D17/001, B24B37/20, B24B37/046, C25F7/00, B24B37/24, B24B37/26, H01L21/76877, C25D5/06, C25D17/14, H01L21/2885|
|European Classification||C25F7/00, H01L21/768C4, B24B37/04D, C25D5/06, H01L21/288E, C25D7/12, B24B37/26, B24B37/20, B24B37/24, C25D17/14|
|Mar 12, 2007||AS||Assignment|
Owner name: NOVELLUS SYSTEMS, INC., CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ASM NUTOOL, INC.;REEL/FRAME:019000/0080
Effective date: 20061204
Owner name: NOVELLUS SYSTEMS, INC.,CALIFORNIA
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:ASM NUTOOL, INC.;REEL/FRAME:019000/0080
Effective date: 20061204
|Jun 15, 2010||CC||Certificate of correction|
|Feb 11, 2013||FPAY||Fee payment|
Year of fee payment: 4